The present invention relates to a display device and a display driver included therein, especially a display driver which can be suitably used for a display device arranged to achieve a display of high image quality by use of a plurality of display driver ICs (IC: Integrated Circuit).
In recent years, the resolution of display devices is becoming increasingly higher, and their sizes are becoming larger. With the progress of such rise in resolution and upsizing, it becomes more difficult to drive a display device by a one-chip display driver, accelerating the tendency to use multiple chips (i.e. a multi-chip) instead thereof. Using multiple chips has the problem that variation among display drivers in output voltage causes a difference in brightness in a display panel and therefore, resulting in decline in image quality.
The Japanese Unexamined Patent Application Publication No. JP-A-2010-26138 discloses a technique for preventing the decline in display quality of a liquid crystal display device operable to activate a display region by drive circuit components in cooperation with one another. According to the technique, based on a gradation reference voltage generated by one drive circuit component, a gradation reference voltage for other ones is generated. Now, it is noted that the gradation reference voltage herein refers to a voltage for producing output voltages to be output to a display panel from the drive circuit components, which is to be used as a reference in producing gradation voltages. The technique is expected to enable the suppression of the variation in output voltage. This is because the output voltages are produced based on a common gradation reference voltage.
International Publication WO01/057839 discloses a technique for preventing the decline of display quality by suppressing a source voltage drop between display drivers in a display device including a display driver of a master mode and a display driver of a slave mode. Gradation voltages are supplied from the display driver of the master mode to the display driver of the slave mode. Providing voltage follower circuits on transmit and receive sides respectively, the output impedance can be lowered, whereas the input impedance can be raised. Therefore, any voltage drop in a gradation voltage is barely caused in a transmission path. Accordingly, it is expected that the decline in display quality can be prevented by preventing the occurrence of bias deviation, and unevenness between blocks in a screen of a display device (see Page 14 of WO01/057839).
The above patent documents JP-A-2010-26138 and WO01/057839 are taken as examples of techniques which offer solutions to the problem of the decline of image quality.